Boosting visible-light-driven photocatalytic performance by heterostructure of S-doped g-C3N4/ MIL-101(Fe)

The construction of heterojunction composite material can take advantage of the complementary advantages of MOF and g-C3N4 to make it possibly have superior performance to its constituent component in terms of the separation of photogenerated carrier, visible light absorption, and the number of active sites, making it a po- tential photocatalytic candidate material. In this work, a sulfur doped g-C3N4/MIL-101(Fe) Z-scheme hetero- structure was successfully fabricated using a facile way integrated hydrothermal and ball-milling methods, of which S-doped g-C3N4 nanosheets were assembled on the surface of MIL-101(Fe) octahedra. By means of characterization of microstructure, chemical states, adsorption and specific surface area, optical and photo - electrochemical properties, and the photocatalytic degradation of methylene blue (MB) under visible light, the photocatalytic activities were systematically evaluated. Furthermore, the photocatalytic mechanism therein was clarified through the electron paramagnetic resonance (ESR) measurements and the active radical capture ex- periments. It was found that the introduction of a certain amount of sulfur doped g-C3N4 nanosheets on the surface of MIL-101(Fe) octahedra efficiently improved the separation and migration rate of photo-induced carriers, consequently resulted in a boost of photocatalytic efficiency for methylene blue (MB) degradation under visible light irradiation and full spectra. Among all photocatalysts MCN-2 presented the best photocatalytic activity for photodegradation of MB. A two-fold increasement was approved compared to bare MIL-101(Fe) under visible light. The superior performance arises from the Z-scheme heterojunction formed between MIL- 101(Fe) and g-C3N4 with favorably matched band energy levels, enabling the separation and fast transfer of the photogenerated carriers. This work provides an effective way for constructing novel photocatalytic systems with efficient activity for refractory pollutant removal.